mechanical aptitude - Page 2

Neil · 11-10-2007, 21:42

WillowTheWhisp · 11-10-2007, 21:46

Hmm, thanks Neil, but I still can't find an illustration of a planetary gear system where the inner cog wheels keep turning when the outer one is held still. How can they?

West Ender · 11-10-2007, 21:47

I only got 56%. Don't bring your car to me when it goes wrong.

cashman · 11-10-2007, 21:52

Quote:

Originally Posted by West Ender

I only got 56%. Don't bring your car to me when it goes wrong.

he he he, you'll do a better job than me westender

jambutty · 11-10-2007, 21:52

Quote:

Originally Posted by entwisi

http://www.forddoctorsdts.com/quizze...alAptitude.php

I got 86%

Anyone beat it?

Shame it doesn't tell you which you got wrong.

I got 94%

It does tell you which you got wrong and it even got one answer wrong itself. Well not so much wrong as having two correct answers and only selecting one of them as correct and of course the other one became incorrect.

Q48 – In a naturally aspirated engine, air enters the cylinder because of

Their answer – From atmospheric pressure pushing it in.

I selected from suction caused by the piston going down, which is the same thing. In fact it is probably more correct than their answer.

The piston moves down and tries to create a vacuum which is equalised by the air pushing in from outside. If the piston didn’t move down there would be nowhere for the air to rush in. The piston doesn’t move down because of the air rushing in but because the crankshaft is still rotating after ignition and pulls it down, thus creating a vacuum, which is equalised by the air rushing in.

So my score should have been 96%.

Lilly · 11-10-2007, 21:55

Wow! Well done, Jambutty.

entwisi · 11-10-2007, 21:56

Willow, the fact that the three small wheels are teh same size allows it to keep moving. if one was a different size then it would lock up as it would be trying to move faster than teh others which wouldn't be possible. as it is each is trying to move in exactly teh same direction and speed so it 'works'

West Ender · 11-10-2007, 21:58

Quote:

Originally Posted by cashman

he he he, you'll do a better job than me westender

Hey, Cashman, between the 2 of us we got 96%. Maybe if we worked together we could

****** it up completely.

SPUGGIE J · 11-10-2007, 22:02

68% but I am useless at theory so I am suprised.

jambutty · 11-10-2007, 22:08

Quote:

Originally Posted by WillowTheWhisp

Hmm, thanks Neil, but I still can't find an illustration of a planetary gear system where the inner cog wheels keep turning when the outer one is held still. How can they?

Because all the internal gears are free to move laterally as well as rotating.

I can’t think of anywhere where such a configuration could be used though.

jambutty · 11-10-2007, 22:10

Quote:

Originally Posted by Lilly

Wow! Well done, Jambutty.

Thanks Lilly but someone of my age and experience in mechanical and electrical engineering should have got 100%, it was that easy.

WillowTheWhisp · 11-10-2007, 22:10

Quote:

Originally Posted by jambutty

Q48 – In a naturally aspirated engine, air enters the cylinder because of

Their answer – From atmospheric pressure pushing it in.

I selected from suction caused by the piston going down, which is the same thing. In fact it is probably more correct than their answer.

I chose suction too and I'm still convinced that is more right than their answer but I can see the logic of 'air pushing into a vacuum' but to my logic air is sucked into a vacuum.

Quote:

Originally Posted by entwisi

Willow, the fact that the three small wheels are teh same size allows it to keep moving. if one was a different size then it would lock up as it would be trying to move faster than teh others which wouldn't be possible. as it is each is trying to move in exactly teh same direction and speed so it 'works'

If the outer rim didn't have cogs then I would agree with you Ian, but the cogs in the outer rim are locked into the cogs in those three small 'planetary' wheels which in turn are locked into the central 'sun'. In any series of gears if one of the cogwheels is held rigid then it prevents the movement of any wheel it interlocks with. So I still say they couldn't possibly move. Now if that outer rim was smooth then of course the three planetary wheels would slide effortlessly within it and their answer would apply, but the rim in the image is not smooth.

WillowTheWhisp · 11-10-2007, 22:12

Cancel that!

I've just had a rethink. I can now visualise them going on a wander within the outer wheel!

MargaretR · 11-10-2007, 22:13

Quote:

Originally Posted by WillowTheWhisp

I chose suction too and I'm still convinced that is more right than their answer but I can see the logic of 'air pushing into a vacuum' but to my logic air is sucked into a vacuum.

If the outer rim didn't have cogs then I would agree with you Ian, but the cogs in the outer rim are locked into the cogs in those three small 'planetary' wheels which in turn are locked into the central 'sun'. In any series of gears if one of the cogwheels is held rigid then it prevents the movement of any wheel it interlocks with. So I still say they couldn't possibly move. Now if that outer rim was smooth then of course the three planetary wheels would slide effortlessly within it and their answer would apply, but the rim in the image is not smooth.

That's decided it - I'm definately not gonna look

steeljack · 11-10-2007, 22:14

Quote:

Originally Posted by WillowTheWhisp

Don't read this if you still want to try the quiz. If you've already done it then please scroll down.
.

agree with you on this , that was my thought (seized up gearbox)